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Hydration characteristics and mechanism analysis of β-calcium sulfate hemihydrate
Highlights The hydration mechanism of hemihydrate was proved to be dissolution and precipitation via in-situ ESEM observation. The detailed dissolution process of hemihydrates were revealed: surface dissolution and particle fragmentation. Gypsum precipitates at the beginning, crystallizes rapidly after 20 min hydration and tends to be stable after 2 h hydration. The hydration reaction of hemihydrate is a process of particle size reduction.
Abstract Although the dissolution/precipitation mechanism for hemihydrate hydration is widely recognized, this study gives more detailed information for the hydration of hemihydrate by in-situ observation using environmental scanning electron microscope (ESEM). The hydration process was also monitored through numerous parameters, including phase, hydration degree, ion concentration, particle size, and morphology evolution with hydration time. The results indicated that the hemihydrate particles are porous containing numerous nanopores. It dissolves from the surface available to water, forming a transient flocculent intermediate with widen pores. Afterwards, large particles break to small particles due to crack connection and then continue to dissolve, leaving a few stubborn spots last to disappear. At the same time, gypsum precipitates in the first few minutes and evolves to the final crystal structure through three main stages. This work not only provides the most direct evidence for the hydration mechanism, but also gives new insights to enrich it further. It is helpful to adjust the hydration process of gypsum plaster and provide a significant reference for modeling.
Hydration characteristics and mechanism analysis of β-calcium sulfate hemihydrate
Highlights The hydration mechanism of hemihydrate was proved to be dissolution and precipitation via in-situ ESEM observation. The detailed dissolution process of hemihydrates were revealed: surface dissolution and particle fragmentation. Gypsum precipitates at the beginning, crystallizes rapidly after 20 min hydration and tends to be stable after 2 h hydration. The hydration reaction of hemihydrate is a process of particle size reduction.
Abstract Although the dissolution/precipitation mechanism for hemihydrate hydration is widely recognized, this study gives more detailed information for the hydration of hemihydrate by in-situ observation using environmental scanning electron microscope (ESEM). The hydration process was also monitored through numerous parameters, including phase, hydration degree, ion concentration, particle size, and morphology evolution with hydration time. The results indicated that the hemihydrate particles are porous containing numerous nanopores. It dissolves from the surface available to water, forming a transient flocculent intermediate with widen pores. Afterwards, large particles break to small particles due to crack connection and then continue to dissolve, leaving a few stubborn spots last to disappear. At the same time, gypsum precipitates in the first few minutes and evolves to the final crystal structure through three main stages. This work not only provides the most direct evidence for the hydration mechanism, but also gives new insights to enrich it further. It is helpful to adjust the hydration process of gypsum plaster and provide a significant reference for modeling.
Hydration characteristics and mechanism analysis of β-calcium sulfate hemihydrate
Chen, Xuemei (author) / Wu, Qihong (author) / Gao, Jianming (author) / Tang, Yongbo (author)
2021-05-20
Article (Journal)
Electronic Resource
English
ACCELERATING THE HYDRATION OF CALCIUM SULFATE HEMIHYDRATE VIA HIGH ENERGY MIXING
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